Enables odometry. (#2)

cartographer_turtlebot2/configuration_files/turtlebot2.lua

@@ -20,7 +20,10 @@ options = {
   tracking_frame = "base_link",
   odom_frame = "odom",
   provide_odom_frame = false,
-  use_odometry_data = false,
+  use_odometry_data = true,
+  use_constant_odometry_variance = true,
+  constant_odometry_translational_variance = 1e-7,
+  constant_odometry_rotational_variance = 1e-7,
   publish_occupancy_grid = false,
   use_horizontal_laser = true,
   use_horizontal_multi_echo_laser = false,